Amputees and other persons with residual limbs often use prosthetic devices, or prostheses. A prosthesis is an artificial device used to replace a missing body part. A transfemoral amputee, a person with a residual limb, or residuum, is missing his lower limb, beginning at his lower thigh (femur) and including the knee through the foot. A prosthesis that simulates the lower limb is often used by a transfemoral amputee. In order to attach the lower limb prosthesis, the residuum is placed into a prosthetic residual limb socket. In order to connect the socket to the lower limb prosthesis, a coupler device is used.
In recent years, use of a plastic or silicone sleeve has gained popularity as a means of suspending the prosthetic socket onto the residuum. A tightly fitting silicone suspension sleeve is rolled onto the residuum. The residuum with the silicone sleeve is then placed into the socket. A pin connects the center of the distal end of a patient's residuum, through a receptacle of the silicone sleeve, to the prosthetic socket and the coupler device via a locking mechanism. When the pin is screwed into the receptacle, it is centered on the end of the residuum. The other end of the pin is inserted into the coupler device that is incorporated into the prosthetic socket. The coupler device also connects the socket to the lower limb prosthesis, which includes a connector, a prosthetic knee joint, a pylon, a tube clamp adapter and a prosthetic foot.
Known locking couplers have the attachment point for the lower limb prosthesis directly in line with the pin and the center of the residuum. This results in co-linearity of the prosthesis with the pin which adversely affects the stability of the prosthesis when there is a flexion contracture of the hip, which occurs often with transfemoral amputees. A need exists for a locking coupler device in which the attachment point for the lower limb prosthesis does not adversely affect the stability of the prosthesis when there is a flexion contraction at the hip, but rather provides for a stable alignment of the prosthesis.
When there is a flexion contracture at the hip, for there to be stable alignment of the prosthesis, the attachment of the prosthetic knee joint and pylon must be along or behind the trochanter-knee-ankle, or TKA, line. A need exists for a coupler device that provides an attachment point of the prosthetic knee joint and pylon along or behind the TKA line.
The requirements that the pin attaches at the center of the distal end of the residuum and that the lower limb prosthesis attaches along or behind the TKA line are mutually exclusive with known locking couplers when a flexion contracture at the hip is present. The pin can be attached at the center of the residuum or the lower limb prosthesis can be attached along the TKA line, but not both. Compromising between these requirements when there is a flexion contraction at the hip results in either 1) inadequate alignment and thus instability if the lower limb prosthesis is not aligned with the TKA line, or 2) inappropriate placement of the attachment pin which restricts donning and doffing the prosthesis if the pin is not attached at the center of the distal end of the residuum.
Because current known locking couplers have the attachment point for the lower limb prosthesis directly in line with the pin and not along the TKA line, the prosthetist is often required to modify the prosthesis to achieve alignment of the knee joint with the TKA line and improve the stability of the prosthesis. To do this, the prosthetist typically creates separate attachment locations on the socket for the pin and for the lower limb prosthesis. The prosthetist attaches a cone of tape or paper to the socket at the location where the lower limb prosthesis is to be attached. The cone is then packed with a filler material which bonds to the socket. When the filler material has dried, the cone can be removed. However, filler material also bonds to the cone and as a result, the cone often cannot be completely removed. Further, the filler material is very heavy. The resulting prosthesis is heavy, bulky and aesthetically unappealing.
A need exists for a locking coupler device that does not require a prosthetist to modify the prosthesis by creating separate attachment locations on the socket for the pin and the attachment point for the rest of the prosthesis. A need also exists for a prefabricated locking coupler device that allows the lower limb prosthesis to attach to the coupler device along or behind the TKA line while allowing the attachment point on the top surface of the locking coupler device to align with the center of the distal end of the residuum.
The sleeve covered residuum is typically drawn into the socket using a tool. A need exists for a coupling device that allows the pin and thus the residuum to be drawn into the socket without a separate tool. A need also exists for a coupler device that is lightweight and aesthetically appealing.